Vapor-compression distillation method and apparatus



Aug. 28, 1956 A. LATHAM, JR-

VAPOR-COMPRESSION DISTILLATION METHOD AND APPARATUS Filed Sept. 2, 1953w mowmmmmiou w I l I NOL Q Dumu muuz mzuxm Emu.

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Wmwww I INVENTOR. ALLE N LATHAM, JR.

HTTORNEYS linited States Patent VAPOR-COMPRESSION DISTILLATION METHODAND APPARATUS Allen Latham, Jr., Jamaica Plain, Mass, assignor, by

mesne asignments, to The Badger Manufacturing Cornpatltly, Cambridge,Mass., a corporation of Massachu se s Application September 2, 1953,Serial No. 378,141

11 Claims. (Cl. 202-75) This invention relates to vapor-compressiondistillation method and apparatus. In vapor-compression distillation,vapor separated from a boiling solution is compressed to a pressure atwhich its condensing temperature is above the boiling point of theboiling solution and is condensed in out-of-contact heat exchangerelation with the boiling solution, thereby returning to thedistillation zone the latent heat of vaporation of the separated vaporso that it is utilized and conserved in the system in the boiling ofadditional solution.

Particularly in connection with the distillation of aqueous solutions,as for example sea water, the entering solution contains air or othernon-condensable gases which during continuance of the distillationbecome separated from the boiling solution and which, beingnoncondensable at the temperatures prevailing in the system, do notcondense along with the vapor. As a result, there is a tendency for thenon-condensable gases to accumulate in the system to such an extent-asto seriously affect its efficiency.

It is an object of this invention to improve upon method and apparatusfor vapor-compression distillation as regards the venting ofnon-condensable gases therefrom. Heretofore, if any means at all hasbeen provided for venting non-condensable gases, such means has been inthe form of a vent line whichis in communication with the condenser heatexchanger wherein the compressed vapor condenses and through which thenon-condensable gases are continuously vented along with some of thevapor.

According to a principal feature of this invention, the non-condensablegases thatbecome separated from the solution undergoingdistillation,.instead of being vented from the system continuously, arecaused to be gradually accumulated in the system during periods ofpredetermined substantial duration and by alternating these periods ofgas accumulation with brief periods of predetermined duration duringwhich the non-condensable gases accumulated during the preceding periodof gas accumulation are vented as a sudden burst. For effecting suchintermittent venting, vent means is employed which comprises a vent linethrough which the non-condensable gases pass in being vented from thecondenser heat exchanger of the system, a valve for controllingthe ventline, and means for opening and closing the valve at predeterminedintervals for periods of predetermined duration for effecting thealternate accumulation of the non-condensable gases and their release asa sudden burst following each period of gas accumulation.

By the employment of method and means whereby the non-condensable gasesare vented intermittently according to this invention from adistillation system of the vapor compression type, it has been foundthat considerable improvement in overall efiiciency is made possi ble inthat the non-condensable gases may be effectively removed from thesystem with a very substantial decrease in the loss of steam or othervapor. Loss of uncondensed steam or other vapor from the systemseriously Patented Aug. 28, 1956 ice affects its efficiency, bothbecause there is a corresponding loss of yield of recovered distillateand because to the extent that the compressed vapor is not condensed inthe condenser heat exchanger its heat of vaporization is lost from thesystem.

In addition, the venting of the non-condensable gases in the form ofintermittent bursts counteracts the occurrence of pockets or otherstagnant zones of noncondensable gases and the venting that isaccomplished is both effective and reliable. Moreover, the venting ofthe non-condensable gases intermittently has the aforesaid advantageswithout'involving any mitigating drawbacks.

A further feature of this invention relates to method steps andapparatus whereby the compressed vapors are caused to become condensedin such a way in relation to the removal of the resulting condensatethat the noncondensable gases that become separated from the condensateduring the condensation of compressed vapor is kept progressively inmotion toward the venting zone from which the non-condensable gases arevented, thereby further minimizing the occurrence of the non-condensablegases in pockets or stagnant zones. Thus, instead of employing a commoncondenser heat exchanger to which the compressed vapor is directed fordistribution and condensation substantially simultaneously throughout,the compressed vapor is directed into what in eifect is a series ofsmall condenser heat exchangers or condensation chambers, through whichthe vapor is successively passed with only partial condensation in theindividual chambers.

Moreover, the means for .drawing otr" condensate from the severalchambers of the system is such that neither vapor nor non-condensablegases are removed with the condensate and the non-condensable' gases arekept in motion by being caused to travelwith' the compressed vapor as itis passedifrom chamber to chamber of the series and into the. lastchamber of the series from which the non-condensable gases are directedthrough the vent line by which they are vented from the system asaforesaid. Preferably thenon-condensable gases are directed from thelast condensation chamber of the series to a distillate level-controlcontainer or an equivalent container or chamber from which they aretakenoh by the vent line.

Further objects, features and advantages of this invention will beapparent in connection with the following more detailed description ofthis invention in connection with the accompanying drawing whichillustrates schematically a typical embodiment of this invention that iscomprised in distillation method and apparatus of the vapor compressiontype.

Referring to the apparatus shown in the drawing, solution to bedistilled is heated in the evaporator chamber 1 to separate vaportherefrom by boiling. The vapor resulting from the boiling ofthesolution is passed through the liquid-vapor separator 2 and isdirected by the low pressure'fline 3 into the compressor 4, which may beof any type adapted to' eifect' the compression of the vapor to apressurei'at yv ich the condensing temperature of the vapor is'above'theboiling point of the solution undergoing distillation andwhic'h may beoperated from any suitable source of power (not shown). The vapor whichhas been compressed by the compressor 4 is directed by the high pressurevapor line 5 to the condenser heat exchanger means which is indicatedgenerally by the reference character 6 and which will be described morein detail hereinbelow. The condensate formed in the condenser heatexchanger 6 is directed by the draw-oil lines 7, the header 8 and theline 9 to the condensate-collecting and levelcontrol container 10. Thecondensate is taken from the container 10 by the line'll, which iscontrolled by the float valve 12 for maintaining constant the level ofthe condensate in thecontainer 10. Before it leaves the systern the notcondensate .is directed through the preheater heat exchanger, which isindicated generally by the reference character 13 and in which thesolution that is being fed into the evaporator chamber by the :feed line14 is preheated.

Hot concentrated solution is taken from the evaporator chamber 1 by thedraw-off line 15, the upper end-of which determines the normal liquidlevel that .is maintained in the evaporator chamber. The line 15 directsthe hot concentrated solution into the concentrated solution-collectingcontainer 16 into which the solution that collects in the liquid-vaporseparator 2 likewise is directed by the line 17. The hot concentratedsolution is taken from the container by the line 18, which is controlledby the float valve .19 for maintaining a constant level in the container16. Before leaving the system by the line 18 the concentrated solutionis passed through the ,preheater heat exchanger 13 for transferring itsheat to the incoming feed.

In the system above described the condensation of the compressed vaporin the condenser heat exchanger .supplies heat for boiling the solutionin the evaporator chamber 1 because of the heat of vaporization that isreturned to the system and in some measure also because of its sensibleheat content as it .leaves the compressor. If desired, auxiliary heatingmeans (not shown) maybe employed in order to compensate for heat lossesfrom the system and heat losses ,may also be minimized by covering theevaporator chamber with a layer of thermal insulation material (notshown);

Referring to the condenser heat exchanger 6 that is comprised in thevapor-compression distillation system, it is to be noted that instead ofbeing in the form of a common unit into which compressed vapor isdirected, the

pressed vapor is shown as entering .the chamber 6a. The

chambers are connected in series by thevapor header means 2% so as tocause the vapor to pass successively through the chambers 6a, 6'b, 6cand 6x with partial condensation thereof in each of the chambers. Whilein the drawing four chambers have been shown connected in series forsuccessive passage of vapor therethrough, .a greater or lesser numbercould be employed as indicated by the break shown in the drawings. Forexample, va typical preferred construction is to provide ten of (thechambers in a single series.

Each of the chambers 6a, 6b and 6c is separately drained by the lines 7to the header 8 from which condensate is taken to thecondensate-coilecting container 10 by the line 9 after having firstpassed the liquid seal trap 21 which maintains the liquid seal legs 22in the lines 7 for efiectively preventing escape of non-condensablegases or vapor through the lines 7.

During distillation non-condensable gases tend to accumulate in thesystem .as a result of the boiI ll .of the solution. While thenon-condensable material may comprise non-condensable vapor, thenon-condensable material is referred to elsewhere herein and in theclaims as non-condensable gases. The non-condensable gases tend toaccumulate in the chamber comprised in the condenser heat exchanger 6.Because none of the noncondensable gases and none of the'vapor can esape through the lines '7 and because the compressed vapor is passedsuccessively through the chambers, the compressed vapors are kept movingat a velocity that is .sufiicientlyhigh to keep non-condensable gasesmoving to the last chamber 6x of the series with avoidance of pockets orstagnant zones in which the non-condensable gases might collect withresultant impairment of the heat exchange elficiency of the condenserheat exchanger. The last chamber 6x of the series is directly connected;at'ithe bottom to the line '9 by the line '23 so as not to be affectedby the liquid seal for the header 18, thereby providing free discharge 4from the chamber 6x of both the non-condensable gases and the condensateformed therein.

While only one series of chambers has been shown disposed in only a partof the evaporator chamber 1, it is to be understood that this has beendone for the purpose of simplifying the drawings and that ordinarily theevaporator chamber has the condenser heatexchanger chambers distributedmore uniformly throughout the body of the solution that is maintained inthe evaporator chamber '1. In such case there may -be additional seriesarrangements of condensation chambers. For example, there may be fourgroups with each group consisting of a series of ten chambers and withthe first chamber of each series connected to the compressor. Allchambers of the several series, except for the last chamber, could insuch case be drained to the header 8 so as to be conmonly affected bythe liquid seal 21. The last chamber in each series could eitherseparately drain into the condensate-collecting container 10 as shown ora common vent header therefor could be provided for directing thedistillate and non-condensable gases therefrom into the container 10.The condensation chambers comprised in the condenser heat exchanger 6may be'of different size as desired. However, by way of further concreteillustration, for providing a vapor-compression distillation .unithaving a capacity of about 300 gallons .per day when employing the fortycondensation chambers arranged in four groups of ten each, each of thechambers could be in the "form of an elliptical chamber about inch thickwhose vertical and horizontal dimensions are about 9 inches and 5 inchesrespectively.

The non-condensable gases which are carried to thecondensate-collectingcontainer 10 are vented therefrom through the line24 in which there is the valve 25, the opening and closing of which atstated intervals is effected automatically. For example, the valve 25may be electrically actuated to open it for the venting of gases throughthe line 24 and outof the system lay-energiz ng a solenoid, the valvenormally being kept closed as by a spring or the like. Suitable solenoidor other valves that are actuatable automatically at stated intervalsare well known. For control-ling the actuation of the valve 25 a timingdevice 26 such as an electric clock may be employed which is adapted toclose and open the switch 27 that controls the electric circuit 28 froman electric current source (not shown) for energizing the solenoid 29when the switch 27 closes the circuit.

In the case of a'unit of the capacity and construction above exemplifiedwhich maintains :a gauge measure within the vaporization chamber ofabout 15 pounds per square inch and a gauge pressure of about 27 poundsper square inch within the condenser heat exchange means duringdistillation of potable water from sea water, typical venting of thenon-condensable gases from the system consists in setting the timingdevice '26 so that the valve '25 remains closed for intervals of tenminutes between which the valve '25 is opened for an interval of fiveseconds, this cycle "being regularly repeated during continuance of thedistillation. Of course, for operation in the manner described the ventline employed as well as the valve that controls it must be ofsufiicient capacity to permit the escape in only a few seconds time of.noncondensable gases that "have accumulated over a much longer period.

-It is apparent that in the operationabove described the non-condensablegases are permitted "to gradually accumulate by preventing their escapeand then are vented in a sudden burst. By venting the non-condensable.gases in this way, it'has been found that the non-condensable gases areeffectively vented and that in so doing the amount of vapor that iscarried therewith is very substantially reduced. Thus, in an operationof the character above exemplified the heat loss resulting fromentrainment of vapor with vented non-condensable gases can be cutto onlyabout 10% of'that which is required in order to accomplish the ventingof non-condensable'gase's'when they are vented by the usual continuousflow method. This constitutes a substantial saving in the amount of heatthat is lost from the system as an incident to obtaining efiectiveventing of the non-condensable gases.

When the venting is accomplished so as to occur in bursts after statedintervals of accumulation of the noncondensable gases, the flow of thenon-condensable gases when the venting occurs is of such suddenness andvolume as to stir up any pockets of non-condensable gas or otherstagnant zones with resultant more effective removal of thenon-condensable gases and in practice it has been found that venting ofthe non-condensable gases according to the invention results in veryreliable and efiective venting. It also has been found in practice thatexcept for the above described advantages-and improvements, thealternate gradual build-up and sudden venting of the non-condensablegases has no perceptible efiect in the V distillation operation.

The practice of this invention is of especial advantage in the case ofvapor-compression distillation units which are of medium to smallcapacity wherein the rates of fluid movement are of such moderation asto be conducive to difficulties because of the occurrence of deadpockets or zones of stagnant non-condensable gases when the conventionalpractice of continuously venting the noncondensable gases is employed. Aunit having the capac ity and construction above described is in thiscategory.

However, this invention may be employed with advantages of the'characterabove described regardlessv of the size and capacity of the unit. Theduration of the intervals during which the non-condensable gasesarealternately accumulated and suddenly released may be varied,

tial benefits, the period of gradual accumulation of thenon-condensables is sixty times the venting period. On the other hand,it would still be consistent with. obtaining good results to extend theperiod for accumulation of condensables to about minutes. If the ventingperiod of 5 seconds is employed under such conditions, the accumulationperiod is about 240 times the venting period, which is about the upperlimit for this relationship if the distillation conditions are to remainsubstantially uniform. For similar reasons, the period during whichnon-condensables are permitted to accumulate ordinarily is not more thanabout minutes. The period of ventingpreferably is brief so thatnon-condensables will emerge in a sudden burst with a flow great enoughto stir up stagnant pockets in regions affected by the opening of thevalve in the vent line while at the same time avoiding undue loss ofvapor. A burst of about 5 to about 10 seconds ordinarily is suitable forthis purpose, the intervening periods during which the non-condensablesare permitted to accumulate being about 60 to about 240 times theduration of the bursts.

While this invention has been described as embodied and employed withone type of vapor-compression distillation unit, it is to be understoodthat this has' been done for purposes of exemplification and that theelements of vapor-compression distillation apparatus in connection withwhich this invention may be employed may take many different forms.Thus, while a preferred type of condenser heat exhanger for use in theevaporator chamber has been described and illustrated, other condenserheat exchanger constructions may be used. However, in such case theadvantages which result from the combination of the condenser heatexchanger means shown and described hereinabove with the venting meansof this invention would not be realized; and in such 6 case, orotherwise, the Vent line means could be com nected directly with anappropriate zone on the interior of the condenser heat exchanger. In theoperation above described by Way of example, the pressures maintainedwithin the evaporator chamber'and Within the condenser heat exchangerare such that concentrated solution and condensate may be removedwithout the employment of pump means to do so. However, particularly ifthe pressures prevailing in the system are lower, or in the case ofunits of larger size, pump means may be employed. Likewise, it is notessential to utilize the condensate-collecting containers 10 and 16 orthe level control means contained therein. It is also apparent thatother means than that shown and described may be employed for effectingintermittent venting of the noncondensable gases at regularly recurringintervals of predetermined duration.

I claim:

1. In a method of distillation wherein vapor is evolved from a solutionin a vaporization zone, the evolved vapor is compressed to a pressure atwhich its condensing temperature is substantially greater than theboiling point of said solution, the compressed vapor is condensed inout-of-contact heat exchange relation with solution in said vaporizationzone, non-condensable gases are separated from the condensate resultingfrom condensation of said vapor, said condensate is directed out of thesystem, concentrated solution is directed out of the said vaporizationzone and out of the system, and fresh solution to be distilled is fedinto said vaporization comprising causing the non-condensable gases tobecome gradually accumulated in the system during periodsofpredetermined substantial duration and alternating said periods of gasaccumulation with brief periods of predetermined duration during whichnon-condensable gases accumulated during the preceding period or" gasaccumulation are vented as a sudden burst.

2. The method according to claim 1 wherein the compressed vapor is movedsuccessively through a series of chambers with deceleration in saidchambers and acceleration during passage from one chamber to the nextduring condensation thereof in out-of-contact heat exchange relationwith said solution toward a venting zone so as to carry saidnon-condensable gases with said compressed vapors during condensationthereof to said zone, said non-condensable gases being vented from saidzone.

3. In a method of distillation wherein vapor is evolved from a solutionin a vaporization zone, the evolved vapor is compressed to a pressure atwhich its condensing temperature is substantially greater than theboiling point of said solution, the compressed vapor is condensed inout-of-contact heat exchange relation with solution in said vaporizationZone, non-condensable gases are separated from the condensate resultingfrom condensation of said vapor, said condensate is directed out of thesystem concentrated solution is directed out of the said vaporizationzone and out of the system, and fresh solution to be distilled is fedinto said vaporization zone; the venting of said non-condensable gasesfrom the system during continuance of distillation by steps comprisingalternately accumulating and venting non-condensable gases byalternately closing and opening a valve in a vent line at predeterminedregularly timed intervals, the duration of the intervals during whichsaid valve is closed for causing accumulation of said non-condensablegases being at least about 60 times the duration of the intervals duringwhich said valve is open for permitting the ventingof saidnon-condensable gases and not being longer than about 30 minutes.

4. The method of claim 3 wherein the duration of the interval duringwhich said valve is closed for causing accumulation of saidnon-condensable gases is from about 5 to about 20 minutes and theduration of the intervals area during which said valve is open forpermitting the vent ing ,of said non-condensable gases is at least aboutseconds. 7

5. The method of claim 3 wherein the period during which saidnon-condensable gases is vented sis of the order of 5 to 10 seconds.

6. A method of distillation which comprises directing vapor evolved froma solution in a vaporization zone to a compressor for compressiontherein, directing vapor compressed by said compressor into.out-of-contaot heat exchange relation with solution in saidvaporization chamber in a series of condensation .chambers through whichsaid vapor is directed sequentially with partial condensation of saidvapor and separation of non-.condensable gases from condensate in eachof said chambers, directing condensate from each of said chambersthrough a liquid seal that prevents escape of non-condensable gases fromsaid condensation chambers except with vapor that is passed from onechamber to the next in said series, thereby moving said gases with saidvapors through said chambers to the last chamber of the series,directing solution to be distilled into said vaporization 'zone,wit-hdrawing concentrated solution from said vaporization zone, andventing non-condensable gases from said last chamber of said seriesintermittently in regularly timed bursts of about 5 to about 10 secondsduration between intervening periods of the order of about 60 to about240 times the duration of said bursts.

7. Distillation apparatus comprising an evaporator chamber, acompressor, means for directing-vapor from said evaporator chamber tosaid compressor for compression therein, a condenser heat exchangerwithin said evaporator chamber adapted to maintain a "fluid therein inout-of-contact heat exchange relation with solution in said evaporatorchamber, means for directing compressed vapor from said compressor intosaid condenser heat exchanger for condensation therein, means fordirecting condensate'resulting from condensation of vapor in saidcondenser heat exchanger from said condenser heat exchanger and out ofthe system, means for withdrawing concentrated solution from saidevaporator chamber, means for introducing solution to be distilled intosaid evaporator chamber, and means for venting non-condensable gasesfrom said condenser heat exchanger; said means for ventingnon-condensable gases comprising a vent line through which said gasespass in being vented from said condenser heat exchanger, valve means forcontrolling the venting of said gases through said vent line and meansfor opening and closing said valve means at predetermined intervals forperiods of predetermined duration.

8. Distillation apparatus comprising an evaporator chamber, acompressor, means for directing vapor -from said evaporator chamber tosaid compressor for compression therein, a condenser heat exchangerwithin said evaporator chamber adapted to maintain a fluid therein inout-of-contact heat exchange relation with solution in said evaporatorchamber, means for directing compressed vapor from said compressor intosaid condenser heat exchanger for condensation therein, means fordirecting condensate resulting from condensation of vapor in saidcondenser heat exchanger from said condenser heat exchanger and out ofthe system, means for withdrawing concentrated solution from saidevaporator chamber, means for introducing solution to 'be distilled intosaid evaporator chamber, and means for venting non-condensahle gasesfrom said condenser heat exchanger; said means for ventingnon-condensable gases comprising a vent line through which said gasespass in being vented from said condenser heat-exchanger, valve means insaid vent line that is responsive to electrical actuation foreifectingsudden opening and sudden closing of said valve means, a timingdevice, electric circuit means operatively connected to said valvemeans, and switch means actuated by said timing device for controllingsaid electric circuit :means whereby responsive to timing automaticallycontrolled by said timing device said valve means normallymaintained'closed and is opened .at regular internals for periods .ofpredetermined duration, said vent dine and said valve means beingadapted. when saidvalve means is suddenly opened to vent non oondensablegases .therethrough .as a sudden burst.

9. .-Dist-illation apparatus comprising an evaporator chamber, acompressor, means for directing vapor from said xevaporator chamber to.said compressor for com- ,pression therein, a condenser heat exchangerwithin said evaporator chamber adapted to maintain a fluid therein inout-.oflcontact :heat exchange relation with solution in said evaporatorchamber, means for directing compressed vapor firom said compressor intosaid condenser heat exchanger ior condensation therein, means for di-.recting condensate resulting from condensation of vapor in saidcondenser heat exchanger from .said condenser heat exchanger and out ofthe system, means for withdrawing concentrated solution from saidevaporator chamber, means ,for introducing solution to be distilled intosaid ievaporator c'hamber, and means for venting inon-condensable gasesitrom said condenser heat .exchanger; .said condenser heat exchangercomprising a series .ofchambers adapted :for condensation of vaportherein .and means .for directing vapor directed from said compressor tosaid condenser heat exchanger successively throughsaid series .ofchambers; said means for directing condensate from said condenser heatexchanger comprising draw-off line means for Withdrawing condensatefrorn each ot the chambers in said series and means for maintainingaliquid seal in said draw-ofi line means that eifective .to preventescape of non-condens- Table gases orvapsr -from said chambers of saidseries vthrough. sa'id draw -ofi line' means except for the chamber attheendjof said seriesremote from the chamber of said series into which.said vapor is initially introduced for sequential travel through saidseries of chambers; and said means for venting non-.condensable gasescomprising a vent line communicating with the chamber at said end ofsaid series for venting non-condensable gases 'tlierefrom'through saidline, a valve for controlling flow through said vent line, andautomatically operable means for maintaining said valve normallysubstantially closed and for opening said valve at predeterminedintervals and for periods of predetermined duration for ventingnoncondensa'ble ,gas accumulated While said valve was maintained closedprior to the opening thereof.

10."Disitillation apparatus comprising an evaporator chamber, acompressor, means for directing vapor from said evaporator chamber tosaid compressor for compression therein, a condenser heat exchangerwithin said evaporator chamber adapted to maintain a fluid therein inout-of-contact heat exchange relation with solution in said'evaporatorchamber, means for directing compressed vapor from said compressor intosaid condenser heat exchanger .for condensation therein, means .fordirecting condensateresulting from condensation of vapor in saidcondenser heat exchanger from said condenser heat exchanger and out ofthe system, means for withdrawing concentrated solution from saidevaporator chamber, means .for introducing solution to 'be distilledinto said evaporator chamber, and means for venting non-condensablegases from said condenser heat exchanger; said means for directingcondensate from said condenser heat exchanger comprising acondensate-collecting container, means for directing condensate andnon-.condensable gases from said condenser heat exchanger into saidcondensate-collecting container and condensate line means for directingcondensate from said condensate-collecting container out of the .system;and said means for venting non-.condensable gases comprising a vent linecommunicating with said condensate-collecting container for ventingtherethrough non-condensable gases from said condensate-collectingcontainer, a valve for controlling flow through said vent line, andautomatically operable means for maintaining said valve normally closedand for opening said valve at predetermined intervals and for periods ofpredetermined duration for venting non-condensable gases accumulatedWhile said valve was maintained closed prior to the opening thereof.

11. Distillation apparatus according to claim 10 which comprises meansfor maintaining susbtantially constant the liquid level of condensate insaid condensate-collecting container.

References Cited in the file of this patent UNITED STATES PATENTSHeinzerling' Jan. 26, 1897 10 Forbes May 24, Le Sucur Dec. 11, SoderlundAug. 17, Soderlund Oct. 10, Harmon May 15, Stone July 17, Mason Apr. 2,Sloan et al. Feb. 19, Kirgan May 11, Cowherd Nov. 21, Cleaver et al. Jan. 9, Filliung May 15, Latham Mar. 18,

FOREIGN PATENTS France Feb. 22, France Ian. 30,

1. IN A METHOD OF DISTILLATION WHEREIN VAPOR IS EVOLVED FROM A SOLUTIONIN A VAPORIZATION ZONE, THE EVOLVE VAPOR IS COMPRESSED TO A PRESSURE ATWHICH ITS CONDENSING TEMPERATURE IS SUBSTANTIALLY GREATER THAN THEBOILING POINT OF SAID SOLUTION, THE COMPRESSED VAPOR IS CONDENSED INOUT-OF-CONTACT HEAT EXCHANGE RELATION WITH SOLUTION IN SAID VAPORIZATIONZONE, NON-CONDENSABLE GASES ARE SEPARATED FROM THE CONDENSATE RESULTINGFROM CONDENSATION OF SAID VAPOR, SAID CONDENSATE IS DIRECTED OUT OF THESAID SYSTEM, CONCENTRATED SOLUTION IS DIRECTED OUT OF THE SAIDVAPORIZATION ZONE AND OUT OF THE SYSTEM, AND FRESH SOLUTION TO BEDISTILLED IS FED INTO SAID VAPORIZATION ZONE; THE VENTING OF SAIDNON-CONDENSABLE GASES FROM THE SYSTEM DURING CONTINUANCE OF DISTILLATIONBY STEPS COMPRISING CAUSING THE NON-CONDENSABLE GASES TO BECOMEGRADUALLY ACCUMULATED IN THE SYSTEM DURING PERIODS OF PREDETERMINEDSUBSTANTIAL DURATION AND ALTERNATING SAID PERIODS OF GAS ACCUMULATIONWITH BRIEF PERIODS OF PREDETERMINED DURATION DURING WHICH NON-CONDENSABLE GASES ACCUMULATED DURING THE PRECEDING PERIOD OF GASACCUMULATION ARE VENTED AS A SUDDEN BURST.